The 93-year-old Graham has a full-page advertisement scheduled to run in 14 state newspapers.

From his home in Montreat, Graham said, "Watching the moral decline of our country causes me great concern. I believe the home and marriage is the foundation of our society and must be protected."

Voters will take to the polls on "Amendment One" on May 8, though early voting has already started.

"At 93, I never thought we would have to debate the definition of marriage," Graham says in the advertisement. "The Bible is clear -- God's definition of marriage is between a man and a woman. I want to urge my fellow North Carolinians to vote for the marriage amendment on Tuesday, May 8. God bless you as you vote."

North Carolina already outlaws gay marriage, but adding the ban to the state constitution would make it much harder to change in the future.

More than 120,000 votes had been cast so far, according to published reports earlier this week.

Both sides in the fight over the proposed amendment held news conferences this week.

In Raleigh, three current and former district attorneys were among those arguing that the amendment won't change how judges apply domestic violence laws.

In Durham, an assistant prosecutor, the head of a state's domestic violence coalition and a family law expert said the opposite: that judges may decide that domestic violence laws don't apply to unmarried people because the amendment is broadly written.

Both sides pointed to Ohio, where the Supreme Court ruled after three years that that state's amendment didn't invalidate domestic violence laws.